The present invention relates to a method of preparing and observing a cross section of a particular spot of a semiconductor device for failure analysis.
FIG. 3 shows a schematic side view of a focused ion beam device, which performs a maskless processing operation and is used for research and development of the most advanced semiconductor devices and fabrication processes. This device is equipped to perform several functions such as a scanning ion microscope function, a maskless etching function and a maskless deposition function.
In view of these functions, this device can be used for observation of a section of a semiconductor device. Namely, a particular cutting edge position is determined by the scanning ion microscope function which is one of the features of this device, then a rectangular groove is formed in a particular spot area by the maskless etching function such that one side of the rectangle is aligned along the cutting edge position to thereby expose a desired section to be observed, and thereafter the sample is inclined so that the section faces toward the incident ion beam to thereby observe the section, again by the scanning ion microscope function.
However, in this method, when preparing a section for observing a contour of an uneven area containing a trench, etc., sputtered material may be redeposited in the trench during the maskless etching, or the uneven contour may effect the prepared section by forming stripes thereon. This results in the drawback that an accurate image of the section cannot be obtained.